This invention relates generally to the ceramic arts and more particularly, to the art application of cermets of high mechanical integrity and retentivity in commercial quantities for industrial and nuclear applications.
Cermets have been previously produced by utilizing a variety of processes under numerous operating conditions which have been adequate for small-scale production. However, these processes have not been suitable for efficient and economic manufacturing of cermets. The desirable mechanical and thermal properties of cermets have created a widespread demand for cermets in various areas such as in the manufacture of machine tools, structural materials, turbine components, valves, ejectors, electrical contacts, bearings, and nuclear-related applications.
The problem of meeting this increasing demand for cermets has been further complicated by the recent short supply and high prices of cobalt, tungsten, and tantalum; the traditional metal "cements" used in the manufacture of cermets. The possible substitution of these alloys with more readily available and less expensive bonding or cementing agents such iron, nickel, molybdenum, aluminum, copper, lead, and tin appears attractive. However, a simple cost-effective process for their incorporation into cermets on a commercial scale has not been previously developed.
The process of the present invention significantly reduces or obviates the aforementioned problem by utilizing a liquid-phase sintering procedure to form cermets of satisfactory metallographic quality in high density. The liquid-phase sintering is accomplished at a commercial scale by using a continuous spray calcination of a urea-dispersed metal solution to produce calcined powders containing the metal oxides which can be, or which are usable in the reduction and liquid-phase sintering operation.